Walker Percy was singularly focused on understanding the structure of symbolic behavior, what he called one of the “essential features of symbolic knowing.” Percy sought understanding of the nature of the symbol in linguistics, sociology, philosophy, theology, and anthropology, but to no avail. Percy had “been at some pains to sketch out an ‘anthropology,’ a theory of man” and hoped to use “CSP’s ‘ontology’ of Secondness and Thirdness (not Firstness) as the ground for a more or less scientific introduction to a philosophical anthropology.” Taking his word that he had been working on such a project and finding no singular work of Percy containing such a sketch suggests that its components might be found scattered throughout his writing. The purpose of this essay is not to provide a possible entire account of his sketch but instead to examine one clear major component of that sketch, “The Lay-Scientific Interface.”